Also known, in order to carry out the transmission of satellite signals in the presence of sources of interference, are systems such as those shown in FIG. 1 using two signals of different types. A first, high-bit-rate signal that is not protected against interference, and a second, low-bit-rate signal that is however protected against interference. This protection against interference may be achieved, for example, by implementing a system regularly changing the frequency of the carrier signal. It is known practice to implement these two signals in two disconnected bands and, when the first, high-bit-rate signal suffers interference, to deactivate the latter and to use the whole of the band for the transmission of the second, low-bit-rate signal. This solution has the drawback of not being optimal. Specifically, the portion of the frequency band used for the transmission of the second, low-bit-rate signal does not make it possible, when there is no interference, to transmit a bit rate equivalent to that which would be available if this portion of the band were used for the transmission of the first, high-bit-rate signal. This solution also has the drawback of causing a break in the continuity of service during the transition from one configuration to another. This break in transmission may be as long as several minutes.
Also known are systems as shown in American patent application US 2011/0249706. These systems consist of stations 101 and a satellite 102. This satellite is used to relay the signals transmitted from one station to the other station. Each station comprises a transmitter 103 and a receiver 104. The transmitters and receivers included in the stations are used to transmit and to receive a first, high-bit-rate signal and a second, low-bit-rate signal that is protected against interference simultaneously and by using the same frequency band. In these systems, the first, high-bit-rate signal can for example follow the recommendations of the standard DVB-S2 (ETSI 302 307). Amongst other things, this standard allows the transmission of a 20 Mbps signal in a 20 MHz bandwidth. For the second, low-bit-rate signal it is possible to use, for example, a signal with a transmission rate of 20 kbit/s using a bandwidth of 2 MHz, this signal being able also to have a device allowing the carrier frequency to move throughout the whole 20 Mhz band used by the first, high-bit-rate signal. The ratio between the spread of the first, high-bit-rate signal and of the second, low-bit-rate signal is in this case 1000, namely a power differential of 30 dB between the first and the second signal. The second, high-bit-rate signal is therefore not disrupted by the first, low-bit-rate signal and thus the second, low-bit-rate signal can cohabit simultaneously in the same frequency band with the first, high-bit-rate signal without causing deteriorations. However, since the configuration of the two signals is fixed, the presence of an interference element renders the first, high-bit-rate signal ineffective, without the resources that are allocated thereto (in particular the power used by the first, high-bit-rate signal) being able to reallocated to the second, low-bit-rate signal. The lack of adaptability to the environmental conditions of this type of system therefore does not make it possible to achieve optimal performance.